Arrangement for the transmission of intelligence



Feb. 18, 1941. L HAGEN 2,232,063

ARRANGEMENT FOR THE TRANSMISSION OF INTELLIGENCE Filed July 22, 1939 LL & M 1w A (tor /15y.

Patented Feb. 18, 1941 UNITED STATES ARRANGEMENT FOR THE TRANSMISSION or INTELLIGENCE Wolfgang Hagen, Berlin, Germany, assignor to G. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany, a company Application July 22, 1939, Serial No. 285,848 In Germany July 22, 1938 3 Claims.

It is a part of prior art that intelligence can be sent over high frequency alternating currents and in casesof two-way communication to use the same carrier frequency for each direction.

5 In such devices modulating circuits have in general been used in which the carrier is suppressed so that it is transmitted neither in interruptions in use nor during the transmission of intelligence. In such circuits a means using the carrier can be employed to transmit the call signal, in which means, for example, a. distortion of the symmetry of the modulation circuit is fed to the outgoing line. The modulation circuits must in all these cases be so regulated, that no carrier frequency is transmitted in a condition of rest, that is, the modulation circuit, must as a rule be of bridge design and be constructed absolutely symmetrical.

The present invention deals with the problem 520 of testing for symmetry circuits employing the same carrier frequency for two-way intelligence trafllc so that from the transmitter to the receiver of the same device the carrier frequency is the same throughout. The unsymmetry which is caused by the call signal release is indicated in the receiving set of the return traffic.

In the accompanying diagram, a possible application of the invention is illustrated. An intermediate relay station is shown in which the 30 regular two-way trafiic from the lines a and b is fed over four-line carrier frequency transmission, according to which it works in both speaking directions of the separate lines with the same carrier frequency and according to which the modulation of the carrier and one sideband are suppressed.

The low frequency coming in on the lines a and b is directed by the branch G into the equivalent line N and into the modulator M through the filter F. This modulation circuit is so symmetrically energized that the carrier, generated by oscillator T, is not permittedtoleave the modulator. The impedances WI and W2, of which WI is variable, are provided to set the modulator for symmetry. The call signal paratus the received keyed carrier frequency is fed through a special amplifier Va and the call signal receiving tube V. This tube is heavily biased negatively so that in a condition of rest no plate current flows. As soon as the keyed carrier frequency reaches the grid, it produces a plate current which flows to the relay E. This relay is so time-delayed that its contact during the whole call signal operation stays closed. The contact el of the relay E, however, operates of itself to interrupt the plate current. The armature of the relay E is operated mechanically only upon the action of the call signal frequency and vibrates independent of the keyed frequency of the carrier. This relay has another contact e2, which changes the polarity of the transformer U, connected to lines (1. and b, from positive to negative and therefore produces in it an alternating current. The relay H lies in'this circuit and, as long as current flows in it in a condition of rest, it is picked up. According to the switching operation of 62 a current is likewise introduced into the second winding of H. When the two windings of the relay H are energized in opposite relation, the armature drops back to normal position. The contact h then operates, releases the relay R from the subscriber line a and b, and connects in the transformer.

At this point the call signal is removed from the received carrier, which is completely suppressed during the rest and speaking intervals.

In order to be able to balance out irregularities in the tubes and rectifiers of the modulator a special test circuit is provided. This circuit short-circuits the lines I and 2 with the contacts SI and S2 and terminates these lines with the impedances W3 and W4, respectively. The outgoing line is also bound to the incoming by the switch S3. In case a part of the carrier is being transmitted through the modulater to the line, 40 the relay E operates and sends the call signal to the subscriber. To hinder the eventual operation of the relay B, it is isolated from the line by the operation of the test switch S4. Through the variation of WI the modulator can be so balanced, that the carrier is completely sup:- pressed, that the call signal receiver is silenced. Through these tests and adjustments the apparatus is made as near as possible ready for operation. It is seen that it is only necessary to operate all the switches SI-Sfl in order to make the desired test and adjustment.

If the terminal station is connected to the low frequency subscriber over a four-wire line without a branch circuit, the call signal results from the suppression of a keying operation, which the contact 1' usually accomplishes. It is thus possible to impress the carrier without interruption upon the line as a call signal. The relay E is replaced by an alarm or ringer in the call receiver.

What is claimed is:

1. A circuit for carrier frequency transmission of intelligence, comprising transmitting and receiving equipment operating upon the same carrier frequency, having a symmetrical modulation. stage adapted to suppress the said carrier, and a connection system for terminating the normal output and input systems of said transmitting and receiving equipment and for connecting the WOLFGANG HAGEN. 

